We now turn to the variance. By definition, the variance calculation boils down to computing two integrals, cf. [1]}, [2]}, [3]},
\(\mathbb {V}\!\left[S\right]&=&\mathbb {E}\!\left[S^{2}\right]-\mathbb {E}^{2}\!\left[S\right]=\mathrm {I_{A}}-\mathrm {I_{B}},\) 
